In a nutshell, guitar tabs are a form a music notation, specific to fretted instruments, that tell the musician which fret to play and not a whole lot else. They can't effectively express certain things that standard sheet music notation can, such as timing. But they are easy to read, easy to write and can give the guitarist a good idea of what fingering to use to play a certain piece of music. And because of this, guitar tabs are a widely accepted and often preferred form of notation.

How to Read a Guitar Tab

Most guitar tabs are made up of 6 lines. Each line represents a string on the guitar. Often times they look like this:

e--------------------------------------------------------------------------------
B--------------------------------------------------------------------------------
G--------------------------------------------------------------------------------
D--------------------------------------------------------------------------------
A--------------------------------------------------------------------------------
E--------------------------------------------------------------------------------

If you can imagine the fretboard of a right handed guitar facing you, you can see that the top line in the guitar tab represents the 1st string on the guitar and the bottom line represents the 6th string. This particular tab doesn't tell us anything though, so we have to fill it out.

e------------------------------------------------------------2-----------2----2--
B-----------1-----------1-----------3-----------3--------3-----------3--------3--
G--------0-----------0-----------0-----------0--------2-----------2-----------2--
D-----2-----------2-----------0-----------0--------0-----------0--------------0--
A--3-----------3-----------2-----------2-----------------------------------------
E--------------------------------------------------------------------------------

Each number in the tab represents the number of the fret to hold down while the particular string the number is on is plucked. '0' represents no fret being held down, or the "open" position. Go ahead and try this tab out. It should sound something like this.

That's basically it. Guitar tabs can only really tell you what to play, not how to play it. The timing and nuances of the song can usually only be determined by listening to the song itself. There are a set of standard symbols you will come across in guitar tabs though, listed below.

How to Write a Guitar Tab

Once you know how to read a guitar tab, not much needs to be said in terms of writing one. There are a few things to keep in mind as you write it though.

1. Avoid writing on just one string. Beginners often tend to put most or all of the notes of a song on one string. At first this can seem like a good thing to do, but you'll quickly find that using all your strings is the way to go. For example, this:

   e--1-5-7---1-5-7---1-5-7-12-10---7-8-7-3-0--
   B-------------------------------------------
   G-------------------------------------------
   D-------------------------------------------
   A-------------------------------------------
   E-------------------------------------------
   

   Would best be written like this:

   e----5-7-----5-7-----5-7-12-10-----------------
   B--6-------6-------6-------------12-13-12-8----
   G-------------------------------------------9--
   D----------------------------------------------
   A----------------------------------------------
   E----------------------------------------------
   

2. Write notes to your audience. Remember, guitar tabs can only tell you what to play, not how. So often times it's helpful to write little notes in your tabs saying things like "Slow down a little here" or "Play this part then jump back up to line 2". It's always good to use notes in your tabs when necessary.
3. Space notes accordingly. It's true that tabs can't effectively express timing, but it's always a good idea to give your audience a general idea of the timing by leaving adequate space between notes.